Interactions and Attachment Pathways between Functionalized Gold Nanorods

Shu Fen Tan, Utkarsh Anand, and Utkur Mirsaidov

ACS Nano 2017 Jan 31. Epub 2017 Jan 31. DOI: 10.1021/acsnano.6b07398

Nanoparticle (NP) self-assembly has been recognized as an important technological process for forming ordered nanostructures. However, the detailed dynamics of the assembly processes remain poorly understood. Using in situ liquid cell transmission electron microscopy, we describe the assembly modes of gold (Au) nanorods (NRs) in solution mediated by hydrogen bonding between NR-bound cysteamine linker molecules. Our observations reveal that by tuning the linker concentration, two different NR assembly modes can be achieved. These assembly modes proceed via the (1) end-to-end and (2) side-to-side attachment of NRs at low and high linker concentrations in solution, respectively. In addition, our time-resolved observations reveal that the side-to-side NR assemblies can occur through two different pathways: (i) prealigned attachment, where two Au NRs prealign to be parallel prior to assembly, and (ii) postattachment alignment, where two Au NRs first undergo end-to-end attachment and pivot around the attachment point to form the side-to-side assembly. We attributed the observed assembly modes to the distribution of linkers on the NR surfaces and the electrostatic interactions between the NRs. The intermediate steps in the assembly reported here reveal how the shape and surface functionalities of NPs drive their self-assembly, which is important for the rational design of hierarchical nanostructures.

Read online: ACS Nano.

CBIS welcomes Prof Ashok Venkitaraman, Director, MRC Cancer Unit, University of Cambridge

Ashok VenkitaramanProfessor Ashok Venkitaraman

CBIS is pleased to welcome Prof Ashok Venkitaraman, Director, MRC Cancer Unit, The Ursula Zoellner Professor of Cancer Research, University of Cambridge

He will be arriving in Singapore on 13 September 2016 and will be with us until 22 October 2016.

He will be spending half of his time at MBI and half at CBIS. His CBIS office is room #02-15. His email is pa-venkitaraman@mrc-cu.cam.ac.uk.

Biography

Ashok is the Ursula Zoellner Professor of Cancer Research at the University of Cambridge, and the Director of the Medical Research Council (MRC) Cancer Unit. He trained in medicine at the Christian Medical College, Vellore, India, before completing his PhD at University College London. Ashok was a faculty member at the Medical Research Council’s Laboratory of Molecular Biology in Cambridge, before appointment to the Zoellner Professorship in 1998.

Ashok is widely recognized for his contributions to understanding the genetics and biology of cancer, particularly in elucidating the impact of genome instability on carcinogenesis and cancer therapy. His research has not only illuminated the fundamental mechanisms governing genome repair, replication and segregation during cell division, but has also provided insight into their connections with cancer pathogenesis and treatment.

Translation of these insights to clinical practice is a major focus in Ashok’s current work. He has been instrumental in establishing initiatives that link chemists, physicists, structural biologists, cancer biologists and clinicians in Cambridge and elsewhere, with the aim to pioneer innovative new approaches for the discovery and early clinical development of next-generation medicines.

Ashok was elected a Fellow of the Academy of Medical Sciences, London, in 2001 and a Member of the EMBO European academy, Heidelberg, in 2004.

Learn more about Prof Venkitaraman.

Visualization of Assembly Intermediates and Budding Vacuoles of Singapore Grouper Iridovirus in Grouper Embryonic Cells

by Yang Liu, Bich Ngoc Tran, Fan Wang, Puey Ounjai, Jinlu Wu & Choy L. Hew

Scientific Reports 6, Article number: 18696 (2016)
doi:10.1038/srep18696

Iridovirid infection is associated with the catastrophic loss in aquaculture industry and the population decline of wild amphibians and reptiles, but none of the iridovirid life cycles have been well explored. Here, we report the detailed visualization of the life cycle of Singapore grouper iridovirus (SGIV) in grouper cells by cryo-electron microscopy (cryoEM) and tomography (ET). EM imaging revealed that SGIV viral particles have an outer capsid layer, and the interaction of this layer with cellular plasma membrane initiates viral entry. Subsequent viral replication leads to formation of a viral assembly site (VAS), where membranous structures emerge as precursors to recruit capsid proteins to form an intermediate, double-shell, crescent-shaped structure, which curves to form icosahedral capsids. Knockdown of the major capsid protein eliminates the formation of viral capsids. As capsid formation progresses, electron-dense materials known to be involved in DNA encapsidation accumulate within the capsid until it is fully occupied. Besides the well-known budding mechanism through the cell periphery, we demonstrate a novel budding process in which viral particles bud into a tubular-like structure within vacuoles. This budding process may denote a new strategy used by SGIV to disseminate viral particles into neighbor cells while evading host immune response.

Read online: Scientific Reports.